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Curious Kids: how many galaxies are there in the universe?

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How many galaxies are there beyond the Milky Way? – Rosella, aged 15, Hong Kong

A galaxy is a massive collection of gas, dust and billions of stars all bound together by the force of gravity. Galaxies are also huge, measuring billions of billions of kilometres across.

To properly understand what a galaxy is, we should start by looking at our own Milky Way galaxy.

Our Sun is just one star out of billions of other stars contained within a galaxy called the Milky Way. In the same way that the Earth orbits the Sun, the Sun also orbits the Milky Way’s centre.

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When we look up at the night sky, the stars we can see with our eyes are all part of the Milky Way. If you’ve been outside on a really clear, dark night, you may have noticed a thin fuzzy band of stars and light stretching across the sky. This is our Milky Way galaxy viewed from the inside out. We see a thin line because our galaxy is shaped like a thin disk, and we’re looking at the edge of the disk.


Curious Kids is a series by The Conversation that gives children the chance to have their questions about the world answered by experts. If you have a question you’d like an expert to answer, send it to curiouskids@theconversation.com and make sure you include the asker’s first name, age and town or city. We won’t be able to answer every question, but we’ll do our very best.


If we look towards the centre of this disk, we see a brighter region called the galactic core. Stars in the core are grouped much closer together, and form a shape that looks like a ball that peeks out from the top and bottom of the disk.

By mapping the positions and motions of the stars in the Milky Way, we can start to build a picture of what our galaxy might look like if we could look down on the disk from above. The overall shape would be a circle.

An artist's impression of the Milky Way galaxy, as seen from the outside. The galaxy has a bright central core and spiral arms that wind out from its centre. The overall shape is similar to a pinwheel

 

An artist’s impression of the Milky Way galaxy, as it would appear if we could see it from the outside.
NASA/JPL-Caltech/ESO/R. Hurt, CC BY

We would see the bright core, which would look reddish-yellow, as the stars here are cooler. Winding out from that core would be a number of spiral arms, bluish in colour because they contain hotter stars. The Milky Way would look a little like a whirlpool.

Beyond the Milky Way

Astronomers are confident that our Milky Way has spiral arms because we see lots of other galaxies like it when we look out into the universe. Most other galaxies that are thin disks similar to our Milky Way also have winding spiral arms. We call these spiral galaxies.

Not every galaxy looks this way, though. Some of the other galaxies we see in the universe look like smooth, fuzzy ovals of light, something between the shape of a basketball and a rugby ball. We call these elliptical galaxies, and they are mostly made up of cooler, redder stars. There are also galaxies that don’t have any particular shape at all. These are called irregular galaxies.

Working out how many galaxies there are in the universe is actually pretty difficult. Many galaxies are too faint or small for us to observe easily, even with the most powerful telescopes. Despite this, astronomers came up with a clever way of working this out. Astronomers pointed the Hubble space telescope at a tiny patch of the sky for 11.3 days and collected the light from galaxies that are both nearby and very distant.

An image of the night sky, containing almost 10,000 galaxies. The galaxies are a variety of shapes and colours
The Hubble Ultra Deep Field image. This image of a tiny patch of sky taken by the Hubble Space Telescope shows almost 10,000 individual galaxies.
NASA, ESA, and S. Beckwith (STScI) and the HUDF Team, CC BY

This tiny patch of sky was full of galaxies, almost 10,000, of all different sizes and shapes. By multiplying this number by the number of times this tiny patch of sky would fit into the entire sky, astronomers came up with an estimate of between about 100 and 200 billion galaxies. This number will almost definitely change, though, as we learn more about our universe in the future.

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SpaceX launch marks 300th successful booster landing – Phys.org

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Credit: Unsplash/CC0 Public Domain

SpaceX sent up the 30th launch from the Space Coast for the year on the evening of April 23, a mission that also featured the company’s 300th successful booster recovery.

A Falcon 9 rocket carrying 23 of SpaceX’s Starlink internet satellites blasted off at 6:17 p.m. Eastern time from Cape Canaveral Space Force Station’s Space Launch Complex 40.

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The first-stage booster set a milestone of the 300th time a Falcon 9 or Falcon Heavy booster made a successful recovery landing, and the 270th time SpaceX has reflown a booster.

This particular booster made its ninth trip to space, a resume that includes one human spaceflight, Crew-6. It made its latest recovery landing downrange on the droneship Just Read the Instructions in the Atlantic Ocean.

The company’s first successful booster recovery came in December 2015, and it has not had a failed booster landing since February 2021.

The current record holder for flights flew 11 days ago making its 20th trip off the .

SpaceX has been responsible for all but two of the launches this year from either Kennedy Space Center or Cape Canaveral with United Launch Alliance having launched the other two.

SpaceX could knock out more launches before the end of the month, putting the Space Coast on pace to hit more than 90 by the end of the year, but the rate of launches by SpaceX is also set to pick up for the remainder of the year with some turnaround times at the Cape’s SLC-40 coming in less than three days.

That could amp up frequency so the Space Coast could surpass 100 launches before the end of the year, with the majority coming from SpaceX. It hosted 72 launches in 2023.

More launches from ULA are on tap as well, though, including the May 6 launch atop an Atlas V rocket of the Boeing CST-100 Starliner with a pair of NASA astronauts to the International Space Station.

ULA is also preparing for the second launch ever of its new Vulcan Centaur rocket, which recently received its second Blue Origin BE-4 engine and is just waiting on the payload, Sierra Space’s Dream Chaser spacecraft, to make its way to the Space Coast.

Blue Origin has its own it wants to launch this year as well, with New Glenn making its debut as early as September, according to SLD 45’s range manifest.

2024 Orlando Sentinel. Distributed by Tribune Content Agency, LLC.

Citation:
SpaceX launch marks 300th successful booster landing (2024, April 24)
retrieved 24 April 2024
from https://phys.org/news/2024-04-spacex-300th-successful-booster.html

This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no
part may be reproduced without the written permission. The content is provided for information purposes only.

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Wildlife Wednesday: loons are suffering as water clarity diminishes – Canadian Geographic

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The common loon, that icon of northern wilderness, is under threat from climate change due to declining water clarity. Published earlier this month in the journal Ecology, a study conducted by biologists from Chapman University and Rensselaer Polytechnic Institute in the U.S. has demonstrated the first clear evidence of an effect of climate change on this species whose distinct call is so tied to the soundscape of Canada’s lakes and wetlands.

Through the course of their research, the scientists found that July rainfall results in reduced July water clarify in loon territories in Northern Wisconsin. In turn, this makes it difficult for adult loons to find and capture their prey — mainly small fish — underwater, meaning they are unable to meet their chicks’ metabolic needs. Undernourished, the chicks face higher mortality rates. The consistent foraging techniques used by loons across their range means this impact is likely echoed wherever they are found — from Alaska to Canada to Iceland.

The researchers used Landsat imagery to find that there has been a 25-year consistent decline in water clarity, and during this period, body weights of adult loon and chicks alike have also declined. With July being the month of most rapid growth in young loons, the study also pinpointed water clarity in July as being the greatest predictor of loon body weight. 

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One explanation for why heavier rainfall leads to reduced water clarity is the rain might carry dissolved organic matter into lakes from adjacent streams and shoreline areas. Lawn fertilizers, pet waste and septic system leaks may also be to blame.

The researchers, led by Chapman University professor Walter Piper, hope to use these insights to further conservation efforts for this bird Piper describes as both “so beloved and so poorly understood.”

Return of the king

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Giant prehistoric salmon had tusk-like teeth for defence, building nests

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The artwork and publicity materials showcasing a giant salmon that lived five million years ago were ready to go to promote a new exhibit, when the discovery of two fossilized skulls immediately changed what researchers knew about the fish.

Initial fossil discoveries of the 2.7-metre-long salmon in Oregon in the 1970s were incomplete and had led researchers to mistakenly suggest the fish had fang-like teeth.

It was dubbed the “sabre-toothed salmon” and became a kind of mascot for the Museum of Natural and Cultural History at the University of Oregon, says researcher Edward Davis.

But then came discovery of two skulls in 2014.

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Davis, a member of the team that found the skulls, says it wasn’t until they got back to the lab that he realized the significance of the discovery that has led to the renaming of the fish in a new, peer-reviewed study.

“There were these two skulls staring at me with sideways teeth,” says Davis, an associate professor in the department of earth sciences at the university.

In that position, the tusk-like teeth could not have been used for biting, he says.

“That was definitely a surprising moment,” says Davis, who serves as director of the Condon Fossil Collection at the university’s Museum of Natural and Cultural History.

“I realized that all of the artwork and all of the publicity materials and bumper stickers and buttons and T-shirts we had just made two months prior, for the new exhibit, were all out of date,” he says with a laugh.

Davis is co-author of the new study in the journal PLOS One, which renames the giant fish the “spike-toothed salmon.”

It says the salmon used the tusk-like spikes for building nests to spawn, and as defence mechanisms against predators and other salmon.

The salmon lived about five million years ago at a time when Earth was transitioning from warmer to relatively cooler conditions, Davis says.

It’s hard to know exactly why the relatives of today’s sockeye went extinct, but Davis says the cooler conditions would have affected the productivity of the Pacific Ocean and the amount of rain feeding rivers that served as their spawning areas.

Another co-author, Brian Sidlauskas, says a fish the size of the spike-toothed salmon must have been targeted by predators such as killer whales or sharks.

“I like to think … it’s almost like a sledgehammer, these salmon swinging their head back and forth in order to fend off things that might want to feast on them,” he says.

Sidlauskas says analysis by the lead author of the paper, Kerin Claeson, found both male and female salmon had the “multi-functional” spike-tooth feature.

“That’s part of our reason for hypothesizing that this tooth is multi-functional … It could easily be for digging out nests,” he says.

“Think about how big the (nest) would have to be for an animal of this size, and then carving it out in what’s probably pretty shallow water; and so having an extra digging tool attached to your head could be really useful.”

Sidlauskas says the giant salmon help researchers understand the boundaries of what’s possible with the evolution of salmon, but they also capture the human imagination and a sense of wonder about what’s possible on Earth.

“I think it helps us value a little more what we do still have, or I hope that it does. That animal is no longer with us, but it is a product of the same biosphere that sustains us.”

This report by The Canadian Press was first published April 24, 2024.

Brenna Owen, The Canadian Press

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