Astronomers estimate the Milky Way galaxy could be filled with up to 100 million black holes.
The electromagnetic counterpart to the Galactic center supermassive black hole, Sgr A*, has been observed in the near-infrared for over 20 years and is known to be highly variable. We report new Keck Telescope observations showing that Sgr A* reached much brighter flux levels in 2019 than ever measured at near-infrared wavelengths. In the K$^\prime$ band, Sgr A* reached flux levels of $\sim6$ mJy, twice the level of the previously observed peak flux from $>13,000$ measurements over 130 nights with the VLT and Keck Telescopes. We also observe a factor of 75 change in flux over a 2-hour time span with no obvious color changes between 1.6 $\mu$m and 2.1 $\mu$m.
Even though the black hole at the center of the Milky Way is a monster, it’s still rather quiet. Called Sagittarius A*, it’s about 4.6 million times more massive than our Sun. Usually, it’s a brooding behemoth. But scientists observing Sgr. A* with the Keck Telescope just watched as its brightness bloomed to over 75 times normal for a few hours.
Astronomers have been watching the black hole at the center of our galaxy for 20 years, and in May, they saw something they’d never seen before.
Our time-dependent Seyfert flare models adequately explain the observations and indicate the Seyfert flare event took place T_o = 3.5 +/- 1 Myr ago.
In 2013, astrophysicist Joss Bland-Hawthorn of the University of Sydney and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D) and colleagues estimated that the event occurred between 1 and 3 million years ago.
Now, more observations taken using the Hubble Space Telescope – and therefore a bigger dataset – have provided even more compelling evidence for the event. And the team has been able to narrow down a timeframe for both when the event occurred, as well as its duration.
Thus it is likely that the Stream emission arose from a `Seyfert flare‘ that was active 1-3 Myr ago, consistent with the cosmic ray lifetime in the Fermi bubbles. Sgr A* activity today is greatly suppressed (70-80 dB) relative to the Seyfert outburst…
The key the astronomers found was actually discovered 20 years old, in the form of a strange glow that astronomers had noticed in the Magellanic Stream. The Magellanic Stream is composed of large clouds of gas – mostly hydrogen – that stretch for light years in the wake of the Milky Way’s two companion Galaxies, the Large and Small Magellanic Clouds. The Stream is about 2 billion years old.
„We didn’t understand the cause. Then suddenly we realised it must be the mark, the fossil record, of a huge outburst of energy from the centre of our Galaxy,“ remarked researcher Joss Bland-Hawthorn in a press release.
ESO’s exquisitely sensitive GRAVITY instrument has added further evidence to the long-standing assumption that a supermassive black hole lurks in the centre of the Milky Way. New observations show clumps of gas swirling around at about 30% of the speed of light on a circular orbit just outside a four million solar mass black hole — the first time material has been observed orbiting close to the point of no return, and the most detailed observations yet of material orbiting this close to a black hole.
The artist impression of the ejection mechanism by the supermassive black hole. Credit: James Josephides (Swinburne Astronomy Productions)
“My favorite part of this discovery is thinking about where this star came from and where it’s going,” said Ji. “It was born in one of the craziest places in the universe, near a supermassive black hole with lots of other nearby star friends; but it’s going to leave our galaxy and die all alone, out in the middle of nowhere. Quite a fall from grace.”
Five million years ago, when humanity’s ancestors were just learning to walk upright, a star was ejected from Sagittarius A*, the supermassive black hole at the center of the Milky Way Galaxy, at a staggering 3.7 million mph. This month, a group of researchers spotted the superfast star traveling relatively close to Earth.
Our sun orbits the galaxy’s center, so many dinosaurs roamed the Earth while the planet was on the other side of the Milky Way.
Our solar system’s orbit keeps us just the right distance from the galaxy’s chaotic center for life to exist.
The word ‘astronomy’ means the direct observations of extra-terrestrial objects. This definition is relevant to photons, neutrinos, and gravitational waves, i.e. massless, neutral and stable particles. But for cosmic ray electrons, protons, and nuclei, the term ‘astronomy’ is used with a certain reservation. Because of the deflections of electrically charged particles in the chaotic interstellar and intergalactic magnetic fields, the information about their original directions pointing to the sites of their production is lost. Instead, on the Earth, we detect an (almost) isotropic flux of cosmic rays contributed by a huge number of galactic and extragalactic sources.
Considerable data and analysis support the detection of one or more supernovae (SNe) at a distance of about 50 pc, ∼2.6 million years ago. This is possibly related to the extinction event around that time and is a member of a series of explosions that formed the Local Bubble in the interstellar medium. We build on previous work, and propagate the muon flux from SN-initiated cosmic rays from the surface to the depths of the ocean. We find that the radiation dose from the muons will exceed the total present surface dose from all sources at depths up to 1 km and will persist for at least the lifetime of marine megafauna. It is reasonable to hypothesize that this increase in radiation load may have contributed to a newly documented marine megafaunal extinction at that time.
(11. Dezember 1983)
At a conference on mass extinctions, held in August at Northern Arizona University in Flagstaff, Dr. Sepkoski said the timing of these events suggested that “there is indeed a statistically significant periodicity in the observed distribution of events of mass or accelerated extinction over the last 250 million years.“ Search for Answers
He confessed this “stumped“ him and Dr. Raup, saying: “We are aware of no documented process with a cycling time approximately 26 million years. But with that long a cycle, we suspect that the forcing agent will not be terrestrial but rather solar or galactic.“
Authors: Laviolette, P. A.
Journal: Earth, Moon, and Planets (ISSN 0167-9295), vol. 37, March 1987, p. 241-286.
For the first time, astronomers followed cosmic neutrinos into the fire-spitting heart of a supermassive blazar.
For the first time ever, scientists have determined the cosmic origin of highest-energy neutrinos. A research group led by IceCube scientist Elisa Resconi, spokesperson of the Collaborative Research Center SFB1258 at the Technical University of Munich (TUM), provides an important piece of evidence that the particles detected by the IceCube neutrino telescope at the South Pole originate from a galaxy four billion light-years away from Earth.
An international team of scientists has found the first evidence of a source of high-energy cosmic neutrinos, ghostly subatomic particles that can travel unhindered for billions of light years from the most extreme environments in the universe to Earth.
The observations, made by the IceCube Neutrino Observatory at the Amundsen–Scott South Pole Station and confirmed by telescopes around the globe and in Earth’s orbit, help resolve a more than a century-old riddle about what sends subatomic particles such as neutrinos and cosmic rays speeding through the universe.
Scientists have captured a ghost-like subatomic particle on Earth, helping to solve a mystery baffling scientists for 100 years.
The so-called “ghost particle” was trapped by researchers in a giant ice cube at the South Pole.
It’s actually a high-energy neutrino, and is the first of its type ever detected by scientists.
Importantly, researchers believe they’ve tracked its likely source: a supermassive black hole that emits light and cosmic rays.
The European Space Agency’s Gaia mission has produced the richest star catalogue to date, including high-precision measurements of nearly 1.7 billion stars and revealing previously unseen details of our home Galaxy.