1 of 14

Space News Update — April 19, 2019 —

Contents

In the News

Story 1: Astronomers Find a Chunk of a Comet Inside a Meteorite

Story 2: Hubble celebrates its 29th birthday with unrivaled view of the Southern

Crab Nebula

Story 3: A Closer Look at Mercury’s Spin and Gravity Reveals the Planet’s Inner Solid

Core

Departments

The Night Sky

ISS Sighting Opportunities

Space Calendar

NASA-TV Highlights

Food for Thought

Space Image of the Week

2 of 14

1. Astronomers Find a Chunk of a Comet Inside a Meteorite

The early days of the Solar System are hard to piece together from our vantage point, billions of years after it happened. Now a team of scientists have found a tiny chunk of an ancient comet inside an ancient meteorite. They say it sheds light on the early days of the Solar System when planets were still forming.

The new research detailing this discovery was published in Nature Astronomy and the lead author is Larry Nittler from the Carnegie Institution. It centers around an ancient meteorite called the LaPaz meteorite that was found in the LaPaz Icefield in Antarctica. It’s a carbonaceous chondrite, some of the most primitive meteorites we know of. About 5% of observed meteorites are of this type.

Observed meteorites are different than what are called “found meteorites.” Observed meteorites are seen by someone, or increasingly, by some automated observer, and are found and examined before they’re subjected to much terrestrial weathering. They’re in more of a pristine state than something that may have been on the surface of Earth for years, decades, or even longer. So they’re desirable scientific objects.

The LaPaz meteorite is a 42 gram rock found by ANSMET, the Antarctic Search for Meteorites, in 2002. It’s in almost pristine condition and hasn’t been changed by weathering. Its official name is LaPaz IceField 02342.

Nittler and the team were studying the meteorite by slicing it thinly and subjecting it to sophisticated chemical and isotope analysis. Inside they found something unusual. There was some very primitive material that bore

3 of 14

resemblance to ancient extraterrestrial dust grains that likely originated in comets that formed in the distant edges of the Solar System.

Asteroid grow gradually by accumulating more and more material. They’re also busted apart by collisions, something that happened a lot more in the early days of the Solar System. About 3 to 3.5 billion years after the Solar System formed, while Earth was still in the process of becoming Earth, this tiny piece of comet, only about one tenth of a millimeter across, was captured by the asteroid.

Then at some point, the asteroid broke apart and LaPaz 02342 fell to Earth, with its tiny passenger protected from destruction as it fell through the atmosphere.

Their analysis showed that this tiny passenger likely came from the icy outer regions of the Solar System, the same place where the Kuiper Belt Objects are, and where many comets come from.

“Because this sample of cometary building block material was swallowed by an asteroid and preserved inside this meteorite, it was protected from the ravages of entering Earth’s atmosphere,” Nittler explained in a press release. “It gave us a peek at material that would not have survived to reach our planet’s surface on its own, helping us to understand the early Solar System’s chemistry.”

The story behind this event helps shed light on the early Solar System formed. Carbonaceous chondrites like LaPaz 02342 formed in an area beyond Jupiter, while comets formed in the distant, icy reaches of the Solar System. Drag from surrounding gas caused the tiny comet particle to migrate from the distant Solar System to the area where carbonaceous chondrites form.

The existence of this tiny piece of rock trapped inside a meteorite shows how the structure of the early Solar System was shaped in the early days of Earth and the other planets.

Source: Universe Today Return to Contents

4 of 14

2. Hubble celebrates its 29th birthday with unrivaled view of the Southern Crab Nebula

5 of 14

This incredible image of the hourglass-shaped Southern Crab Nebula was taken to mark the NASA/ESA Hubble Space Telescope's 29th anniversary in space. The nebula, created by a binary star system, is one of the many objects that Hubble has demystified throughout its productive life. This new image adds to our understanding of the nebula and demonstrates the telescope's continued capabilities.

On 24 April 1990, the NASA/ESA Hubble Space Telescope was launched on the spaceshuttle Discovery. It has since revolutionised how astronomers and the general public see the Universe. The images it provides are spectacular from both a scientific and a purely aesthetic point of view.

Each year the telescope dedicates a small portion of its precious observing time to take a special anniversary image, focused on capturing particularly beautiful and meaningful objects. This year's image is the Southern Crab Nebula, and it is no exception.

This peculiar nebula, which exhibits nested hourglass-shaped structures, has been created by the interaction between a pair of stars at its centre. The unequal pair consists of a red giant and a white dwarf. The red giant is shedding its outer layers in the last phase of its life before it too lives out its final years as a white dwarf. Some of the red giant's ejected material is attracted by the gravity of its companion.

When enough of this cast-off material is pulled onto the white dwarf, it too ejects the material outwards in an eruption, creating the structures we see in the nebula. Eventually, the red giant will finish throwing off its outer layers, and stop feeding its white dwarf companion. Prior to this, there may also be more eruptions, creating even more intricate structures.

Astronomers did not always know this, however. The object was first written about in 1967, but was assumed to be an ordinary star until 1989, when it was observed using telescopes at the European Southern Observatory's La Silla Observatory. The resulting image showed a roughly crab-shaped extended nebula, formed by symmetrical bubbles of gas and dust.

These observations only showed the outer hourglass emanating from a bright central region that could not be resolved. It was not until Hubble observed the Southern Crab in 1998 that the entire structure came into view. This image revealed the inner nested structures, suggesting that the phenomenon that created the outer bubbles had occurred twice in the (astronomically) recent past.

It is fitting that Hubble has returned to this object twenty years after its first observation. This new image adds to the story of an active and evolving object and contributes to the story of Hubble's role in our evolving understanding of the Universe.

Source: Phys.org Return to Contents

6 of 14

3. A Closer Look at Mercury’s Spin and Gravity Reveals the Planet’s Inner Solid Core

How do you explore the interior of a planet without ever touching down on it? Start by watching the way the planet spins, then measure how your spacecraft orbits it — very, very carefully. This is exactly what NASA planetary scientists did, using data from the agency’s former mission to Mercury.

It has long been known that Mercury and the Earth have metallic cores. Like Earth, Mercury’s outer core is composed of liquid metal, but there have only been hints that Mercury’s innermost core is solid. Now, in a new study, scientists from NASA’s Goddard Space Flight Center in Greenbelt, Maryland have found evidence that Mercury’s inner core is indeed solid and that it is very nearly the same size as Earth’s inner core.

Some scientists compare Mercury to a cannonball because its metal core fills nearly 85 percent of the volume of the planet. This large core — huge compared to the other rocky planets in our solar system — has long been one of the most intriguing mysteries about Mercury. Scientists had also wondered whether Mercury might have a solid inner core.

The findings of Mercury’s solid inner core, described in Geophysical Research Letters, certainly adds to a better understanding of Mercury, but there are larger ramifications. Just how similar, and how different, the cores of the planets are may give us clues about how the solar system formed and how rocky planets change over time.

“Mercury’s interior is still active, due to the molten core that powers the planet’s weak magnetic field, relative to Earth’s,” said Antonio Genova, an assistant professor at the Sapienza University of Rome who led the research while at NASA Goddard. “Mercury’s interior has cooled more rapidly than our planet’s. Mercury may help us predict how Earth’s magnetic field will change as the core cools."

To figure out what the core of Mercury is made of, Genova and his colleagues had to get, figuratively, closer. The team used several observations from the MESSENGER (Mercury Surface, Space Environment, GEochemistry and Ranging) mission to probe the interior of Mercury. The researchers looked, most importantly, at the planet’s spin and gravity.

The MESSENGER spacecraft entered orbit around Mercury in March 2011, and spent four years observing this nearest planet to our Sun until it was deliberately brought down to the planet’s surface in April 2015.

Radio observations from MESSENGER were used to determine the gravitational anomalies (areas of local increases or decreases in mass) and the location of its rotational pole, which allowed scientists to understand the orientation of the planet.

Each planet spins on an axis, also known as the pole. Mercury spins much more slowly than Earth, with its day lasting about 58 Earth days. Scientists often use tiny variations in the way an object spins to reveal clues about its internal structure. In 2007, radar observations made from Earth revealed small shifts in the spin of Mercury, called librations, that proved some of Mercury’s core must be liquid-molten metal. But observations

7 of 14

of the spin rate alone were not sufficient to give a clear measurement of what the inner core was like. Could there be a solid core lurking underneath, scientists wondered?

Gravity can help answer that question. “Gravity is a powerful tool to look at the deep interior of a planet because it depends on the planet’s density structure,” said Sander Goossens, a Goddard researcher who worked with Genova on this study.

As MESSENGER orbited Mercury over the course of its mission, and got closer and closer to the surface, scientists recorded how the spacecraft accelerated under the influence of the planet’s gravity. The density structure of a planet can create subtle changes in a spacecraft’s orbit. In the later parts of the mission, MESSENGER flew about 120 miles above the surface, and less than 65 miles during its last year. The final low-altitude orbits provided the best data yet, and allowed for Genova and his team to make the most accurate measurements about the internal structure of Mercury yet taken.

Genova and his team put data from MESSENGER into a sophisticated computer program that allowed them to adjust parameters and figure out what the interior composition of Mercury must be like to match the way it spins and the way the spacecraft accelerated around it. The results showed that for the best match, Mercury must have a large, solid inner core. They estimated that the solid, iron core is about 1,260 miles (about 2,000 kilometers) wide and makes up about half of Mercury’s entire core (about 2,440 miles, or nearly 4,000 kilometers, wide). In contrast, Earth’s solid core is about 1,500 miles (2,400 kilometers) across, taking up a little more than a third of this planet’s entire core.

“We had to pull together information from many fields: geodesy, geochemistry, orbital mechanics and gravity to find out what Mercury’s internal structure must be,” said Goddard planetary scientist Erwan Mazarico, who also helped Genova reveal Mercury’s solid core.

The fact that scientists needed to get close to Mercury to find out more about its interior highlights the power of sending spacecraft to other worlds. Such accurate measurements of Mercury’s spin and gravity were simply not possible to make from Earth. Additionally, this result used data collected by MESSENGER over several years, information that’s available for all scientists to use. New discoveries about Mercury are practically guaranteed to be waiting in MESSENGER’s archives, with each discovery about our local planetary neighborhood giving us a better understanding of what lies beyond.

“Every new bit of information about our solar system helps us understand the larger universe,” said Genova.

Source: NASA Return to Contents

8 of 14

The Night Sky Friday, April 19

• Full Moon (exact at 7:12 a.m. Eastern Daylight Time). This evening look for Spica upper right of the Moon by about a fist and a half at arm's length, and brighter Arcturus about twice that far to the Moon's upper left.

Saturday, April 20

• About an hour after dark, the Pointer stars forming the end of the Big Dipper's bowl point straight down toward Polaris. Face north and look way up. Polaris is about three fists at arm's length from the Pointers.

Sunday, April 21

• Arcturus shines brightly in the east early these evenings. The Big Dipper, very high in the northeast, points its curving handle to the lower right more or less toward it.

Arcturus forms the pointy end of a long, narrow kite asterism formed by the brightest stars of Bootes, the Cowherd. The kite is currently lying on its side to Arcturus's left. The head of the kite, at the far left, is bent slightly upward. The kite is 23° long, about two fists at arm's length. Look soon after dark before the Moon rises.

Monday, April 22

• The Lyrid meteor shower, usually weak to begin with, will be largely spoiled by bright moonlight during the shower's early-morning active hours tonight and tomorrow night.

• However, if you are outside in the hours before dawn, you'll find Jupiter just a degree or two from the waning gibbous Moon (as seen from the longitudes of the Americas). Jupiter is currently 1,800 times farther than the Moon — which it why it looks like just a dot even though it's 40 times larger in diameter.

Tuesday, April 23

• Right after dark, the Sickle of Leo stands vertical high in the south. Its bottom star is Regulus, the brightest of Leo. Leo himself is walking horizontally westward. The Sickle forms his front leg, chest, mane, and part of his head. Denebola, about two and a half fists left of Regulus, is his tail-tip.

• As dawn begins to brighten on Wednesday morning, the waning gibbous Moon shines almost midway between Jupiter to its right and Saturn to its left.

Source: Sky & Telescope Return to Contents

9 of 14

ISS Sighting Opportunities

For Denver: No sightings for Denver through 4/25 Sighting information for other cities can be found at NASA’s Satellite Sighting Information NASA-TV Highlights (all times Eastern Daylight Time) April 19, Friday 4 a.m. - Coverage of the rendezvous and capture of the Northrop Grumman Cygnus CRS-11 cargo craft at the Space Station; capture scheduled at approximately 5:30 a.m. EDT (All Channels) 7 a.m. - Coverage of the Installation of the Northrop Grumman Cygnus CRS-11 cargo craft to the Unity Module of the Space Station (All Channels) 10 a.m. – SpaceCast Weekly (All Channels) 11:10 a.m. – International Space Station In-Flight Event with Military Officers Magazine with NASA astronaut Nick Hague (All Channels) (SpaceCast Weekly will be preempted on Friday, April 19 by other programming) 2 p.m. – International Space Station Expedition 60-61 Crew News Conference (Skvortsov, Morgan, Parmitano) (All Channels) TBD – International Space Station Expedition 59 In-Flight Event with Military Officers Magazine with NASA astronauts Anne McClain and Nick Hague (All Channels)

April 22, Monday 3 p.m. – NASA Science Live: Our Weird Home (All Channels)

Watch NASA TV on the Net by going to the NASA website. Return to Contents

10 of 14

Space Calendar • Apr 19 - Comet P/2017 S8 (PANSTARRS) Closest Approach To Earth (2.299 AU) • Apr 19 - Comet C/2017 X1 (PANSTARRS) Closest Approach To Earth (4.248 AU) • Apr 19 - Aten Asteroid 522684 (2016 JP) Near-Earth Flyby (0.049 AU) • Apr 19 - Asteroid 2409 Chapman Closest Approach To Earth (1.588 AU) • Apr 19 - Asteroid 1489 Attila Closest Approach To Earth (1.776 AU) • Apr 19 - Asteroid 7000 Curie Closest Approach To Earth (2.063 AU) • Apr 19 - Gertrude Bacon's 145th Birthday (1874) • Apr 20 - [Apr 17] BeiDou 3 CZ-3A Launch • Apr 20 - Comet P/2002 EJ57 (LINEAR) At Opposition (2.535 AU) • Apr 20 - Comet P/2007 Q2 (Gilmore) At Opposition (4.062 AU) • Apr 20 - Apollo Asteroid 2019 GZ3 Near-Earth Flyby (0.026 AU) • Apr 20 - Apollo Asteroid 469219 (2016 HO3) Closest Approach To Earth (0.151 AU) • Apr 20 - Apollo Asteroid 14827 Hypnos Closest Approach To Earth (1.222 AU) • Apr 20 - Asteroid 23638 Nagano Closest Approach To Earth (1.323 AU) • Apr 20 - Asteroid 1913 Sekanina Closest Approach To Earth (2.098 AU) • Apr 20 - Asteroid 8889 Mockturtle Closest Approach To Earth (2.478 AU) • Apr 20 - Asteroid 2848 ASP Closest Approach To Earth (2.820 AU) • Apr 20 - Amor Asteroid 9172 Abhramu Closest Approach To Earth (2.936 AU) • Apr 20 - Vincenzo Cerulli's 160th Birthday (1859) • Apr 21 - Easter Sunday • Apr 21 - Comet P/2005 GF8 (LONEOS) Closest Approach To Earth (2.077 AU) • Apr 21 - Apollo Asteroid 2019 GM Near-Earth Flyby (0.050 AU) • Apr 21 - Apollo Asteroid 2016 WQ3 Near-Earth Flyby (0.073 AU) • Apr 21 - Asteroid 5608 Olmos Closest Approach To Earth (1.625 AU) • Apr 21 - Asteroid 243097 Batavia Closest Approach To Earth (1.688 AU) • Apr 21 - Asteroid 13667 Samthurman Closest Approach To Earth (1.787 AU) • Apr 21 - Asteroid 39382 Opportunity Closest Approach To Earth (3.557 AU) • Apr 21 - Jupiter Trojan 3451 Mentor At Opposition (4.192 AU) • Apr 21 - Jean-Bapiste Biot's 245th Birthday (1774) • Apr 21 - Jan van Riebeeck's 400th Birthday (1619)

• Apr 22 - [Apr 15] Earth Day • Apr 22 - Lyrids Meteor Shower Peak • Apr 22 - Comet 17P/Holmes At Opposition (3.400 AU) • Apr 22 - Comet P/2017 U3 (PANSTARRS) Perihelion (4.444 AU) • Apr 22 - Amor Asteroid 2019 FV2 Near-Earth Flyby (0.040 AU) • Apr 22 - Atira Asteroid 2015 DR215 Closest Approach To Earth (1.305 AU) • Apr 22 - Asteroid 67 Asia Closest Approach To Earth (1.452 AU) • Apr 22 - Asteroid 11836 Eileen Closest Approach To Earth (2.127 AU) • Apr 22 - Immanuel Kant's 295th Birthday (1724) • Apr 23 - Comet P/2010 TO20 (LINEAR-Grauer) At Opposition (4.846 AU) • Apr 23 - Comet C/2017 F2 (PANSTARRS) At Opposition (6.684 AU) • Apr 23 - Apollo Asteroid 2019 GM4 Near-Earth Flyby (0.023 AU) • Apr 23 - Apollo Asteroid 478784 (2012 UV136) Near-Earth Flyby (0.074 AU) • Apr 23 - Asteroid 4352 Kyoto Closest Approach To Earth (2.240 AU)

Source: JPL Space Calendar Return to Contents

11 of 14

Food for Thought

Independent report concludes 2033 human Mars mission is not feasible

An independent report concluded that NASA has no chance of sending humans to Mars by 2033, with the earliest such a mission could be flown being the late 2030s.

The report, while completed prior to the March 26 speech where Vice President Mike Pence directed NASA to return humans to the moon by 2024, does offer insights into how much a lunar return might cost and how it fits into long-term plans to send humans to Mars.

NASA contracted with the Science and Technology Policy Institute (STPI) to prepare the report, which Congress directed NASA to perform in the 2017 NASA authorization act. That bill called specifically for a technical and financial assessment of “a Mars human space flight mission to be launched in 2033.”

STPI, at NASA’s direction, used the strategy the agency had laid out in its “Exploration Campaign” report, which projects the continued use of the Space Launch System and Orion and development of the lunar Gateway in the 2020s. That would be followed by the Deep Space Transport (DST), a crewed spacecraft that would travel from cislunar space to Mars and back. NASA would also develop lunar landers are related system to support crewed missions to the lunar surface, while also working on systems for later missions to the surface of Mars.

That work, the STPI report concluded, will take too long to complete in time to support a 2033 mission. “We find that even without budget constraints, a Mars 2033 orbital mission cannot be realistically scheduled under NASA’s current and notional plans,” the report states. “Our analysis suggests that a Mars orbital mission could be carried out no earlier than the 2037 orbital window without accepting large technology development, schedule delay, cost overrun, and budget shortfall risks.”

12 of 14

That schedule is driven by the technology risks associated in particular with the Deep Space Transport, including life support systems and propulsion, that require long lead times. A mission to Mars launching in 2033, the report concluded, would need to have critical technologies tested by 2022, which is unlikely. Moving ahead without completing those technologies first, the report stated, will “dramatically increase technology and schedule risks for the DST and could force the DST design to be revised if any one of these technology testing programs reveals problems.”

Moreover, initial “Phase A” students of the overall DST would need to start in fiscal year 2020, which is also unlikely because trade studies on the DST design have yet to begin. The STPI report also warns that attempting to reduce schedules by not using NASA’s existing standard practices for program development “would lead to very high technology, schedule, and cost overrun risk.”

“As such,” the report concludes, “a mission to Mars orbit in 2033 is infeasible from a technology development and schedule perspective.” The next launch window, in 2035, was also deemed infeasible because of technology development work, pushing the earliest possible date for flying the mission to the following launch window in 2037.

STPI also estimated the cost of carrying out this first Mars mission in 2037. The report estimated the total cost of just those elements needed for the Mars mission, including SLS, Orion, Gateway, DST and other logistics, at $120.6 billion through fiscal year 2037. Of that total, $33.7 billion has been spent to date on SLS and Orion development and associated ground systems.

That total includes $29.2 billion for the DST, a figure that the report acknowledges is a very rough estimate given the few details about the design that could be used to project its development cost. Instead, STPI used the cost of developing Orion as a proxy for the DST. By contrast, the report estimated the cost of the Gateway at less than $6 billion for its various modules, in part because some of the modules would be contributed by international partners at effectively no cost to NASA.

Lunar landing costs

That Mars mission is part of an overall human spaceflight program with total costs through 2037 of $217.4 billion. That includes the Mars mission costs as well as operations in low Earth orbit and development of Mars surface systems needed for future missions.

It also includes a series of missions to land on the moon. The report projected the first human landing to take place in 2028, the date NASA was aiming for prior to Pence’s speech in March. Four more missions, one per year, would follow through 2032.

The report uses the three-stage lunar lander approach that NASA studied last year, with a reusable ascent stage and transfer vehicle and expendable descent stages. Development of the landers and refueling systems alone would cost nearly $8 billion to cover that series of five crewed landings as well as an earlier uncrewed test. An additional $12 billion covers SLS and Orion costs, as well as other launches to transport the landers, propellant and other cargo. Those totals don’t include other costs, such as development of the SLS, Orion and Gateway themselves.

The report, dated February 2019, was completed prior to the announcement of the 2024 lunar landing goal, and thus does not address costs of such an effort. The report estimated that the first lunar landing mission would cost an estimated $2.44 billion in launch and hardware costs, plus several billion in development costs for the landers.

Congressional reaction

13 of 14

The report has received a relative muted reaction on Capitol Hill, in part because it has been overtaken by events, namely plans to accelerate the first human landing to 2024 that will affect other elements over the overall exploration plan.

Rep. Kendra Horn (D-Okla.), chairwoman of the House space subcommittee, did mention in it in prepared remarks for an April 2 heating by the full House Science Committee on the NASA budget request.

“According to the report, it’s clear that getting to the surface of Mars in the 2030s is impossible under this Administration’s current approach to exploration,” she wrote in those remarks. “Moreover, the report acknowledges what many on this Committee have been surmising during past hearings — namely, that there is no actual Plan for a human Mars mission.”

While NASA has, since Pence’s speech, focused on how it will develop an architecture for a 2024 moon landing, it has not neglected Mars entirely. “Why do we go to the moon? Why is that so important?” NASA Administrator Jim Bridenstine asked in an April 9 speech at the 35th Space Symposium in Colorado Springs. “Well, because we’re keeping our eyes on the horizon. The moon is a proving ground. It’s the best place for us to live and work on another world so that we can ultimately go to Mars.”

In that speech, he cited both ongoing Mars missions and future ones, such as the Mars 2020 rover, as preludes to human missions there. He also argued that going to the moon in 2024 would allow an earlier human mission to Mars. “People say, ‘Why are you accelerating a mission to the moon?’ Well, because it accelerates a mission to Mars,” he said.

He made a similar argument in that April 2 hearing. “We want to achieve a Mars landing in 2033,” he said. “In order to do that, we have to accelerate other parts of the program. The moon is a big piece of that.”

He also alluded to the STPI report in his testimony. “We can move up the Mars landing by moving up the moon landing,” he said. The agency hasn’t disclosed details about how that will be possible, including the technology development issues for the Deep Space Transport, independent of a moon landing, that the STPI report concluded prevented a Mars mission from being ready by 2033.

Those comments, though, assuaged Rep. Ed Perlmutter (D-Colo.), a member of the committee and an outspoken advocate for a 2033 Mars mission who regularly displays a “Mars 2033” bumper sticker at hearings such as this one.

“Initially, when I came in, I was disappointed in the report that came back on the pathway to Mars,” Perlmutter said at that hearing, referring to the STPI report’s conclusion that a 2033 Mars mission is not feasible. “It was really disappointing to me.”

However, he said he was encouraged by Bridenstine’s comments that a 2033 Mars mission is possible if a moon landing takes place in 2024. “I’m okay with that because I think it accelerates the effort to get to Mars,” he said of the 2024 goal of a human return to the moon, “which I think is the underlying driving force here.”

Source: SpaceNews.com Return to Contents

14 of 14

Space Image of the Week

The Leo Trio Image Credit & Copyright: Markus Bauer

Explanation: This group is popular in the northern spring. Famous as the Leo Triplet, the three magnificent galaxies gather in one field of view. Crowd pleasers when imaged with even modest telescopes, they can be introduced individually as NGC 3628 (left), M66 (bottom right), and M65 (top). All three are large spiral galaxies but they tend to look dissimilar because their galactic disks are tilted at different angles to our line of sight. NGC 3628, also known as the Hamburger Galaxy, is temptingly seen edge-on, with obscuring dust lanes cutting across its puffy galactic plane. The disks of M66 and M65 are both inclined enough to show off their spiral structure. Gravitational interactions between galaxies in the group have left telltale signs, including the tidal tails and warped, inflated disk of NGC 3628 and the drawn out spiral arms of M66. This gorgeous view of the region spans almost two degrees (four full moons) on the sky. The field covers about a million light-years at the trio's estimated distance of 30 million light-years. Of course the spiky foreground stars lie within our own Milky Way.

Source: APOD Return to Contents