Is the black hole at the center of the Milky Way becoming more active? It’s been getting some attention lately. There is ten-fold increase of X-ray flares from Sagittarius A* since an object called G2 made a close approach.
Here’s the NASA / Chandra press release:
Three orbiting X-ray space telescopes have detected an increased rate of X-ray flares from the usually quiet giant black hole at the center of our Milky Way galaxy after new long-term monitoring.
Scientists are trying to learn whether this is normal behavior that was unnoticed due to limited monitoring, or these flares are triggered by the recent close passage of a mysterious, dusty object.
The Andromeda galaxy is an easy telescope target it is a relatively bright magnitude 3.4 and very large. I am in a new location and seem to have pretty dark skies, could it be a binocular target? I’m soon to find out.
Hubble took a look and found open star clusters in Andromeda 2.5 million light-years away. Our own Milky Way has many star clusters and I have a favorite – the Double Cluster.
The image description from Hubblesite:
[Top] — This is a Hubble Space Telescope mosaic of 414 photographs of the nearest major galaxy to our Milky Way galaxy, the Andromeda galaxy (M31). The vast panorama was assembled from nearly 8,000 separate exposures taken in near-ultraviolet, visible, and near-infrared light. Embedded within this view are 2,753 star clusters. The view is 61,600 light-years across and contains images of 117 million stars in the galaxy’s disk.
[Bottom-Left] — An enlargement of the boxed field in the top image reveals myriad stars and numerous open star clusters as bright blue knots. Hubble’s bird’s-eye view of M31 allowed astronomers to conduct a larger-than-ever sampling of star clusters that are all at the same distance from Earth, 2.5 million light-years. The view is 4,400 light-years across.
[Bottom-Right] — This is a view of six bright blue clusters extracted from the field. Hubble astronomers discovered that, for whatever reason, nature apparently cooks up stars with a consistent distribution from massive stars to small stars (blue supergiants to red dwarfs). This remains a constant across the galaxy, despite the fact that the clusters vary in mass by a factor of 10 and range in age from 4 million to 24 million years old. Each cluster square is 150 light-years across.
Credit: NASA, ESA, J. Dalcanton, B.F. Williams, and L.C. Johnson (University of Washington), the PHAT team, and R. Gendler
A beautiful image from ESA’s Herschel Space Observatory.
See a larger version here at ESA.
Credit: ESA/Herschel/PACS/SPIRE/HOBYS Key Programme consortium
Fierce flashes of light ripple through delicate tendrils of gas in this new image, from ESA’s Herschel space observatory, which shows the dramatic heart of a large and dense cosmic cloud known as Mon R2. This cloud lies some 2700 light-years away and is studded with hot, newly-formed stars.
Packed into the bright centre of this region are several hot ‘bubbles’ of ionised hydrogen, associated with newborn stars situated nearby. Here, gas heated to a temperature of 10 000 °C quickly expands outwards, inflating and enlarging over time. Herschel has explored the bubbles in Mon R2, finding them to have grown over the course of 100 000 to 350 000 years.
The star in this image is around ten times the radius of our Sun and is about 9 times as massive. Even though it is losing mass thanks to those strong stellar winds the star could have enough mass left over to explode as a supernova in the next few hundred thousand years – or so. As for the sizes above, the values depend on distance. Distance is difficult and why missions like Gaia are so important.
Here’s the ESA/Hubble/NASA press release:
Here we see the spectacular cosmic pairing of the star Hen 2-427 — more commonly known as WR 124 — and the nebula M1-67 which surrounds it. Both objects, captured here by the NASA/ESA Hubble Space Telescope are found in the constellation of Sagittarius and lie 15,000 light-years away.
The star Hen 2-427 shines brightly at the very center of this explosive image and around the hot clumps of surrounding gas that are being ejected into space at over 93,210 miles (150,000 km) per hour.
Hen 2-427 is a Wolf–Rayet star, named after the astronomers Charles Wolf and Georges Rayet. Wolf–Rayet are super-hot stars characterized by a fierce ejection of mass.
The nebula M1-67 is estimated to be no more than 10,000 years old — just a baby in astronomical terms — but what a beautiful and magnificent sight it makes.
Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt
Text credit: European Space Agency
A colorful nebula seems a great way to start the week.
Hubble’s view of the Little Gem Nebula (via NASA):
This colorful bubble is a planetary nebula called NGC 6818, also known as the Little Gem Nebula. It is located in the constellation of Sagittarius (The Archer), roughly 6,000 light-years away from us. The rich glow of the cloud is just over half a light-year across — humongous compared to its tiny central star — but still a little gem on a cosmic scale.
When stars like the sun enter “retirement,” they shed their outer layers into space to create glowing clouds of gas called planetary nebulae. This ejection of mass is uneven, and planetary nebulae can have very complex shapes. NGC 6818 shows knotty filament-like structures and distinct layers of material, with a bright and enclosed central bubble surrounded by a larger, more diffuse cloud.
Scientists believe that the stellar wind from the central star propels the outflowing material, sculpting the elongated shape of NGC 6818. As this fast wind smashes through the slower-moving cloud it creates particularly bright blowouts at the bubble’s outer layers.
Hubble previously imaged this nebula back in 1997 with its Wide Field Planetary Camera 2, using a mix of filters that highlighted emission from ionized oxygen and hydrogen. This image, while from the same camera, uses different filters to reveal a different view of the nebula.
Image credit: ESA/Hubble & NASA, Acknowledgement: Judy Schmidt
Text credit: European Space Agency
A nice (and timely) follow-up to a post last week talking a little about metallicity. This planetary nebula has no “common name” that I can find. Looks a bit like a Jellyfish to me.
Here’s ESA description:
This NASA/ESA Hubble Space Telescope image shows a planetary nebula named NGC 6153, located about 4,000 light-years away in the southern constellation of Scorpius (The Scorpion). The faint blue haze across the frame shows what remains of a star like the sun after it has depleted most of its fuel. When this happens, the outer layers of the star are ejected, and get excited and ionized by the energetic ultraviolet light emitted by the bright hot core of the star, forming the nebula.
It’s always nice when a Hubble release features a scientist at a home town school. Bravo!
Quasars are the light fantastic. They are the brightest beacons in the universe, blazing across space with the intrinsic brightness of one trillion suns. Yet the objects are not vast galaxies, but they appear as pinpoint sources in the biggest telescopes of today — hence the term “quasar” for quasi-stellar object. Discovered in the 1960s, it took more than two decades of research to come to the conclusion that quasars are produced by the gusher of energy coming from over-fed supermassive black holes inside the cores of very distant galaxies. And, most quasars bloomed into a brief existence 12 billion years ago.
The big question has been, why? What was happening in the universe 12 billion years ago? The universe was smaller and so crowded that galaxies collided with each other much more frequently than today. Astronomers using Hubble’s near-infrared vision tested this hypothesis by looking at dusty quasars where their glow was suppressed by dust, allowing a view of the quasar’s surroundings. Hubble’s sharp vision revealed chaotic collisions between galaxies that gave birth to quasars by fueling a supermassive central black hole.
“The Hubble observations are definitely telling us that the peak of quasar activity in the early universe is driven by galaxies colliding and then merging together,” said Eilat Glikman of Middlebury College in Vermont. “We are seeing the quasars in their teenage years, when they are growing quickly and all messed up.”
Read the full story.
This is an artist concept of kind of a weird acting star (Artist rendition: NASA, ESA, and G. Bacon (STScI)). Wolf-Rayet stars are massive stars. We even know of one WR star that has the mass of around 265 of our Sun located in the Large Magellanic Cloud about 165,000 light-years from us in the R136 super cluster called R136a1. In our own Milky Way there are about 500 WR stars. That’s so big it’s almost hard to imagine.
Then there is Nasty 1, this intro from Hubblesite (link goes to full story):
Astronomers have spent decades trying to determine the oddball behavior of an aging star nicknamed “Nasty 1” residing in our Milky Way galaxy. Nasty 1 was identified as a Wolf-Rayet star, a rapidly evolving star that is much more massive than our sun. The star loses its hydrogen-filled outer layers quickly, exposing its super-hot and extremely bright helium-burning core.
But Nasty 1 doesn’t look like a typical Wolf-Rayet star. Astronomers using NASA’s Hubble Space Telescope had expected to see a bipolar outflow of twin lobes of gas from the star, perhaps similar to those emanating from the massive star Eta Carinae. The astronomers were surprised, however, to find a pancake-shaped disk of gas encircling the star. The vast disk is nearly 1,000 times the diameter of our solar system. It may have formed from the interaction between Nasty 1 and an unseen companion star. The star may represent a brief transitory stage in the evolution of extremely massive stars. Nasty 1’s nickname was derived from its catalog name of NaSt1.
This image is the Boomerang Nebula, a product of ALMA and Hubble. The Boomerang is 5,000 light-years away in the constellation Centaurus. Click the image above to see the Hubble image without the ALMA data, you will also see why it also has the name of the Bow Tie Nebula.
The Boomerang is a protoplanetary nebula, a confusing term because it does not mean it is forming planets, it’s between the (asymptotic) giant phase and the planetary nebula phase. The cool thing about the Boomerang is not just cool it is cold. It is the coldest place we know of, 1 degree Kelvin and that’s -272.15 C / -457.87 F, the atoms are just barely moving!
I also can’t help thinking I saw an episode of Star Trek with a creature that looks a lot like the ALMA addition.
Image: Bill Saxton; NRAO/AUI/NSF; NASA/Hubble; Raghvendra Sahai