Giant Black Hole Inside Small Galaxy Surprises Scientists

A computer simulation of the collision of two black holes detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, in Washington in February, 2016. Photo: Reuters/Caltech/MIT/Ligo Laboratory
A computer simulation of the collision of two black holes detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, in Washington in February, 2016. Photo: Reuters/Caltech/MIT/Ligo Laboratory
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Giant Black Hole Inside Small Galaxy Surprises Scientists

A computer simulation of the collision of two black holes detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, in Washington in February, 2016. Photo: Reuters/Caltech/MIT/Ligo Laboratory
A computer simulation of the collision of two black holes detected by the Laser Interferometer Gravitational-Wave Observatory, or Ligo, in Washington in February, 2016. Photo: Reuters/Caltech/MIT/Ligo Laboratory

A tiny galaxy orbiting at the outskirts of the Milky Way appears to have a giant black hole at its center, comparable to that of the much larger Milky Way itself, and scientists are surprised.

The Leo I dwarf galaxy is some 820,000 light-years from Earth, and astronomers believe its mass was about 15 to 30 million times the mass of our sun. That's tiny compared to the Milky Way, which is estimated to weigh as much as 1.5 trillion suns and whose disk is over 100,000 light-years wide.

However, the study published in the latest issue of the Astrophysical Journal, unexpectedly found that at the heart of the little Leo I sits a black hole that is nearly as large as the one at the heart of the entire Milky Way. The discovery defies expectations as astronomers believed giant black holes grow from collisions between galaxies and should correspond with the galaxy's size.

"There is no explanation for this kind of black hole in dwarf spheroidal galaxies," María José Bustamante, an astronomy researcher at the University of Texas, and lead author of the new paper, said in a statement quoted by the Live Science website.

The discovery came as scientists originally set out to measure the amount of dark matter in Leo I using the Virus-W instrument on the University of Texas' 2.7-meter Harlan Telescope.

Virus-W measures the motion of stars in small galaxies around the Milky Way and infers the amount of dark matter in those galaxies from those motions.

Dark matter is the completely invisible material that resists gravity. Scientists can measure its concentrations in the universe based on its effects on orbits and velocities of nearby stars. The more dark matter in the star's orbit, the faster it travels.

When the team ran data gathered in the observations through their computer models, they found that Leo I appears to have basically no dark matter but a black hole at its center as heavy as 3 million suns. These findings surprised the scientists as the Sagittarius A* black hole at the center of the Milky Way is only 25% larger.



Researchers Document Huge Drop in African Elephants in a Half Century

 Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
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Researchers Document Huge Drop in African Elephants in a Half Century

 Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo
Elephants walk at the Amboseli National Park in Kajiado County, Kenya, April 4, 2024. REUTERS/Monicah Mwangi/File Photo

African elephants are Earth's largest land animals, remarkable mammals that are very intelligent and highly social. They also are in peril. Fresh evidence of this comes in a study that documents alarming population declines at numerous sites across the continent over about a half century.

Researchers unveiled on Monday what they called the most comprehensive assessment of the status of the two African elephant species - the savanna elephant and forest elephant - using data on population surveys conducted at 475 sites in 37 countries from 1964 through 2016.

The savanna elephant populations fell by about 70% on average at the surveyed sites and the forest elephant populations dropped by about 90% on average at the surveyed sites, with poaching and habitat loss the main drivers. All told, there was a 77% population decrease on average at the various surveyed sites, spanning both species, Reuters reported.

Elephants vanished at some sites while their populations increased in other places thanks to conservation efforts.

"A lot of the lost populations won't come back, and many low-density populations face continued pressures. We likely will lose more populations going forward," said George Wittemyer, a Colorado State University professor of wildlife conservation and chair of the scientific board of the conservation group Save the Elephants, who helped lead the study published in the journal Proceedings of the National Academy of Sciences.

Poaching typically involves people killing elephants for their tusks, which are sold illegally on an international black market driven mostly by ivory demand in China and other parts of Asia. Agricultural expansion is the top factor in habitat loss.

The forest elephant population is estimated to be about a third that of savanna elephants. Poaching has affected forest elephants disproportionately and has ravaged populations of both species in northern and eastern Africa.

"We have lost a number of elephant populations across many countries, but the northern Sahel region of Africa - for example in Mali, Chad and Nigeria - has been particularly hard hit. High pressure and limited protection have culminated in populations being extirpated," Wittemyer said.

But in southern Africa, elephant populations rose at 42% of the surveyed sites.

"We have seen real success in a number of places across Africa, but particularly in southern Africa, with strong growth in populations in Botswana, Zimbabwe and Namibia. For populations showing positive trends, we have had active stewardship and management by the governments or outside groups that have taken on a management role," Wittemyer said.

The study did not track a continent-wide population tally because the various surveys employed different methodologies over different time frames to estimate local elephant population density, making a unified head count impossible. Instead, it assessed population trends at each of the surveyed sites.

A population estimate by conservationists conducted separately from this study put the two species combined at between 415,000 and 540,000 elephants as of 2016, the last year of the study period. It remains the most recent comprehensive continent-wide estimate.

"The loss of large mammals is a significant ecological issue for Africa and the planet," said conservation ecologist and study co-author Dave Balfour, a research associate in the Centre for African Conservation Ecology at Nelson Mandela University in South Africa.

The world's third extant elephant species, the slightly smaller Asian elephant, faces its own population crisis, with similar factors at play as in Africa.

Of African elephants, Wittemyer said, "While the trends are not good, it is important to recognize the successes we have had and continue to have. Learning how and where we can be successful in conserving elephants is as important as recognizing the severity of the decline they have experienced."

Wittemyer added of these elephants: "Not only one of the most sentient and intelligent species we share the planet with, but also an incredibly important part of ecosystems in Africa that structures the balance between forest and grasslands, serves as a critical disperser of seeds, and is a species on which a multitude of other species depend on for survival."