July 2025: What's in the Southern Hemisphere sky this month?

It doesn't happen often that Mercury ranks as the planetary highlight of the evening sky, but July is an exception. The solar system's smallest major planet reaches greatest elongation on July 4, when it lies 26° east of the Sun and stands 11° high in the northwest an hour after sunset. Mercury shines at magnitude 0.5, making it an easy target in the gathering twilight.

Take some time each evening to observe the innermost planet through your telescope. The first half of July finds Mercury drawing closer to the Sun, so we see more of its night side and thus a pleasing crescent phase. The inner world also is approaching Earth, so it grows larger in the eyepiece. On July 1, Mercury appears 7.6″ across and 46 percent lit. On the 15th, it spans 9.9″ and the Sun illuminates 22 percent of its Earth-facing hemisphere. The planet disappears in the Sun's glow in late July.

Unlike Mercury, Mars remains on view all month. The Red Planet drifts slowly eastward through Leo during July, crossing into western Virgo in the month's final days. Mars glows at magnitude 1.5 and appears more conspicuous for its ruddy color than for its brightness. A telescope reveals a disappointing sight: a featureless disk only 5″ across.

Only an hour or so after Mars sets in the west, Saturn rises in the east. The ringed planet lies against the backdrop of southern Pisces the Fish. Its eastward motion comes to a halt on July 14, when it begins to move westward in anticipation of its September opposition.

The best views of Saturn through a telescope occur when it climbs high in the sky during the early morning hours. The planet shows an 18″-diameter disk surrounded by a ring system that spans 41″ and tilts 3.6° to our line of sight. Also keep an eye out for Saturn's brightest moons: Titan, Tethys, Dione, and Rhea.

You can use Saturn as a guide for finding Neptune at the beginning of July. On the 1st, the ice giant planet is located 1.0° north of the ringed planet. Neptune shines at magnitude 7.8, making it bright enough to be seen through binoculars, although a telescope will be needed to discern its blue-gray color.

Early risers can enjoy wonderful views of Venus in the northeast before daybreak. The planet shines at magnitude –4.1 among the background stars of Taurus, appearing 100 times brighter than the Bull's luminary, 1st-magnitude Aldebaran. The planet passes 3° north of the star July 14, but a better view comes the morning before when Venus appears nearly on top of Epsilon (ε) Tauri and marks the northern tip of the V-shaped Hyades star cluster. At month's end, the planet makes a brief and rare excursion into far northern Orion.

As Venus' orbit carries it away from Earth this month, the inner planet appears smaller and more fully illuminated through a telescope. It begins July sporting a disk 18″ in diameter and 64 percent lit. By month's end, its disk spans 14″ and appears three-quarters lit.

Jupiter remains lost in the Sun's glare in early July but climbs into view to the lower right of Venus after midmonth. Shining at magnitude –1.9, it easily pierces the twilight glow. Although a telescope shows the planet's 33″-diameter disk at month's end, poor seeing near the horizon will render details hard to see. Better views await in the coming months.

A waxing gibbous Moon occults 1st-magnitude Antares on July 7. Observers in the western parts of Western Australia, the Indian Ocean, and parts of South Africa can see this event. From Perth, Antares disappears at 19h24m UT (on the morning of July 8) and reappears at 20h19m UT.

The Starry Sky

Midwinter is an excellent time to observe the far southern sky. The magnificent Milky Way arches high in the south, passing through Crux the Cross with Carina the Keel to its right and the Pointers (Alpha [α] and Beta [β] Centauri) in Centaurus the Centaur to its left.

Alpha Cen makes a fine telescopic object. The third-brightest star in the night sky quite easily resolves into a double star. The primary one is a near twin to the Sun, while the secondary is a bit smaller and cooler. A third member of the system, the 11th-magnitude red dwarf Proxima Centauri, lies some 2° away from the main pair. Proxima's main claim to fame is as the closest star to the Sun. Father Jean Richaud discovered the duplicity of Alpha Centauri from Pondicherry, India, in 1689. Robert Innes first spotted Proxima in 1915.

Surprisingly, perhaps, Beta Cen - whose proper name is Hadar - also is a triple system. Dutch astronomer Joan Voûte discovered Beta's main companion in 1935. Beta Centauri B lies 1.3″ from the primary. Glowing at 4th magnitude, it's extremely hard to spot next to the magnitude 0.6 primary.

In the 1960s, observations of the primary showed variations in its light curve that suggested it was a member of a binary system, making Beta a triple system. To me, R.R. Shobbrook and J.W. Robertson wrote the most significant paper on the star's duplicity in 1968. They used the famous 74-inch telescope at Australia's Mount Stromlo Observatory, which was destroyed by devastating fires in 2003. I was reflecting on those observations last year when I attended the observatory's centenary celebration.

Through those observations and the work of many others, astronomers have established that Beta Centauri A is indeed a close double star. Both suns are blue-white giants that orbit each other every 357 days.

Star Dome

The map below portrays the sky as seen near 30° south latitude. Located inside the border are the cardinal directions and their intermediate points. To find stars, hold the map overhead and orient it so one of the labels matches the direction you're facing. The stars above the map's horizon now match what's in the sky.

The all-sky map shows how the sky appears at:

9 p.m. July 1

8 p.m. July 15

7 p.m. July 31

Planets are shown at midmonth

July 2025 - Southern Hemisphere Download

The post July 2025: What's in the Southern Hemisphere sky this month? appeared first on newsrealtime Magazine .

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A strange bright burst in space puzzled astronomers for over a year. Now, they have solved the mystery.

On June 13 last year around midday, my colleagues and I were scanning the skies when we thought we had discovered a strange and exciting new object in space. Using a huge radio telescope, we spotted a blindingly fast flash of radio waves that appeared to be coming from somewhere inside our galaxy.

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After a year of research and analysis, we have finally pinned down the source of the signal—and it was even closer to home than we had ever expected.

A surprise in the desert

Our instrument was located at Inyarrimanha Ilgari Bundara—also known as the Murchison Radio-astronomy Observatory—in remote Western Australia, where the sky above the red desert plains is vast and sublime.

We were using a new detector at the radio telescope known as the Australian Square Kilometer Array Pathfinder—or ASKAP —to search for rare flickering signals from distant galaxies called fast radio bursts .

We detected a burst . Surprisingly, it showed no evidence of a time delay between high and low frequencies—a phenomenon known as " dispersion ."

This meant it must have originated within a few hundred light years of Earth. In other words, it must have come from inside our galaxy—unlike other fast radio bursts which have come from billions of light years away.

A problem emerges

Fast radio bursts are the brightest radio flashes in the universe, emitting 30 years' worth of the sun's energy in less than a millisecond—and we only have Hints of how they are produced.

Some theories suggest they are produced by " magnetars "—the highly magnetized cores of massive, dead stars—oro arise from cosmic collisions between these dead stellar remnants. Regardless of how they occur, fast radio bursts are also a precise instrument for mapping out the so-called "missing matter" in our universe.

When we went back over our recordings to take a closer look at the radio burst, we had a surprise: the signal seemed to have disappeared. Two months of trial and error went by, until the problem was found.

ASKAP consists of 36 antennas that can be combined to function like a single enormous zoom lens spanning six kilometers. Similar to a zoom lens on a camera, if you attempt to capture an image of something too close, it will appear blurry. It was only by excluding some of the antennas from the analysis—artificially decreasing the size of our "lens"—that we were able to ultimately create an image of the burst.

We weren't excited by this—in fact, we were disappointed. No astronomical signal could be close enough to cause this blurring.

This meant it was probably just radio-frequency " interference —an astronomer's term for human-made signals that corrupt our data.

It's the kind of junk data we'd normally throw away.

Yet the burst had us intrigued. For one thing, this burst was fast The fastest known fast radio burst lasted about 10 millionths of a second. This burst consisted of an extremely bright pulse lasting a few billionths of a second, and two dimmer after-pulses, for a total duration of 30 nanoseconds.

So where did this amazingly short, bright burst come from?

A zombie in space?

We already knew the direction it came from, and we were able to use the blurriness in the image to estimate a distance of 4,500 km. And there was only one thing in that direction, at that distance, at that time—a derelict 60-year-old satellite called Relay 2 .

Relay 2 was one of the first ever telecommunications satellites. Launched by the United States in 1964, it was operated until 1965, and its onboard systems had failed by 1967.

But how could Relay 2 have produced this burst?

Some satellites, presumed dead, have been observed to reawaken They are known as "zombie satellites."

But this was no zombie. No system on board Relay 2 had ever been able to produce a nanosecond burst of radio waves, even when it was alive.

We think the most likely cause was an "electrostatic discharge." As satellites are exposed to electrically charged gases in space known as plasmas, they can become charged— just like when your feet rub on carpet And that accumulated charge can suddenly discharge, with the resulting spark causing a flash of radio waves.

Electrostatic discharges are common, and are known to damage the spacecraft . However, all known electrostatic discharges last thousands of times longer than our signal, and occur most commonly when the Earth's magnetosphere is highly active. And our magnetosphere was unusually quiet at the time of the signal.

Another possibility is a strike by a micrometeoroid—a tiny piece of space debris—similar to that experienced by the James Webb Space Telescope in June 2022.

According to our calculations, a 22 micro-gram micrometeoroid traveling at 20 km per second or more and hitting Relay 2 would have been able to produce such a strong flash of radio waves. But we estimate the chance that the nanosecond burst we detected was caused by such an event to be about 1%.

Plenty more sparks in the sky

Ultimately, we can't be certain why we saw this signal from Relay 2. What we do know, however, is how to see more of them. When looking at 13.8 millisecond timescales—the equivalent of keeping the camera shutter open for longer—this signal was washed out, and barely detectable even to a powerful radio telescope such as ASKAP.

But if we had searched at 13.8 nanoseconds, any old radio antenna would have easily seen it. It shows us that monitoring satellites for electrostatic discharges with ground-based radio antennas is possible. And with the number of satellites in orbit growing rapidly , finding new ways to monitor them is more important than ever.

But did our team eventually find new? astronomical signals? You bet we did . And there are no doubt plenty more to be found.

This article is republished from The Conversation under a Creative Commons license. Read the original article .

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